Corrosion-resistant bond pad and integrated device

Abstract

The invention provides an integrated device with corrosion-resistant capped bond pads. The capped bond pads include at least one aluminum bond pad on a semiconductor substrate. A layer of electroless nickel is disposed on the aluminum bond pad. A layer of electroless palladium is disposed on the electroless nickel, and a layer of immersion gold is disposed on the electroless palladium. A capped bond pad and a method of forming the capped bond pads are also disclosed.

Description

FIELD OF THE INVENTION This invention relates generally to semiconductor processing. More specifically, the invention relates to a corrosion-resistant capped bond pad for integrated circuits and sensors, and methods of forming the capped bond pad at the wafer, die or assembly level. BACKGROUND OF THE INVENTION Aluminum bond pads are used extensively in electronics assembly applications such as integrated circuits and silicon-based sensors. Although aluminum wirebonds well, aluminum bond pads on integrated circuits are susceptible to corrosion under standard environmental test conditions. This corrosion can cause performance degradation and product failure when the joint between a gold wire and an aluminum pad degrades and fails. A proposed solution for protecting metal bond pads of conventionally packaged, non-hermetic chip-on-board assemblies is to encapsulate the bonded die with a silicone compound, which helps isolate the pads from aggressive environmental conditions such as h...

AI Technical Summary

Problems solved by technology

Although aluminum wirebonds well, aluminum bond pads on integrated circuits are susceptible to corrosion under standard environmental test conditions.

This corrosion can cause performance degradation and product failure when the joint between a gold wire and an aluminum pad degrades and fails.

Unfortunately, dispensing and curing the silicone is a time-consuming process.

The silicone, having a higher dielectric constant and loss tangent than air, may cause a degradation of high-frequency and radio-frequency (RF) performance.

In addition, silicone encapsulations are difficult to remove completely, precluding rework and repair.

Unfortunately, fluorosilicones can be difficult to remove and can degrade RF performance when used over high frequency and RF devices.

The film or coating, which is vacuum-deposited, cannot be used with chip-on-board (COB) applications and is an expensive process, particularly when done at the assembled device level.

This approach does not address the RF performance and repairability problems for COB applications.

While this approach is effective, it is not compatible with chip-on-board assembly applications and adds bulk.

This, more complex process is incompatible with MEMS sensing requirements and does not address the RF performance degradation problem for COB applications.

This partial solution, however, is limited because many die in the RF section and most of the die in the digital section of an assembly have aluminum bond pads, and therefore must still be encapsulated for corrosion resistance.

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